Bottom Line:
The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion.Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences.The drug-fiber complexes exhibited sustained release.

ABSTRACTIon-exchange fibers were different from conventional ion-exchange resins in their non-cross-linked structure. The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion. Therefore, this work aimed to investigate the load and release characteristics of five model drugs with the strong cationic ion-exchange fiber ZB-1. Drugs were loaded using a batch process and released in United States Pharmacopoeia (USP) dissolution apparatus 2. Opposing exchange kinetics, suitable for the special structure of the fiber, were developed for describing the exchange process with the help of thermodynamics, which illustrated that the load was controlled by an ionic reaction. The molecular weight was the most important factor to influence the drug load and release rate. Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences. The drug-fiber complexes exhibited sustained release. Different kinds and concentrations of counter ions or different amounts of drug-fiber complexes in the release medium affected the release behavior, while the pH value was independent of it. The groundwork for in-depth exploration and further application of ion-exchange fibers has been laid.

Mentions:
Figure 2 shows two types of curves of model drugs loading into the ion-exchange fibers at 25°C. Type one exhibited a very fast loading rate – 30 minutes was enough to reach equilibrium, while the loading amount was small, and the drugs included atenolol, tramadol, and venlafaxine; type two exhibited a slow loading rate – several days were needed to reach equilibrium, while the loading amount was larger, and the drugs included sinomenine and diltiazem. Opposing exchange kinetics captured the characteristics of the loading curves of atenolol and sinomenine, at three different temperatures, quite successfully (Figure 3), illustrating that the model could interpret the loading behaviors. Table 2 depicts the comparison between the experimental results (Qt) and the theoretical predictions (Qp) for atenolol at varying temperatures. The residual variations were small between the rates of ion-exchange and ionic reaction, suggesting that the ionic reaction was the rate-determining step for the loading process of ion-exchange fibers. However, for type two drugs at low temperature, the calculated values were somewhat higher than the observed ones, illustrating that there were other factors influencing the exchange rate under some conditions.

Mentions:
Figure 2 shows two types of curves of model drugs loading into the ion-exchange fibers at 25°C. Type one exhibited a very fast loading rate – 30 minutes was enough to reach equilibrium, while the loading amount was small, and the drugs included atenolol, tramadol, and venlafaxine; type two exhibited a slow loading rate – several days were needed to reach equilibrium, while the loading amount was larger, and the drugs included sinomenine and diltiazem. Opposing exchange kinetics captured the characteristics of the loading curves of atenolol and sinomenine, at three different temperatures, quite successfully (Figure 3), illustrating that the model could interpret the loading behaviors. Table 2 depicts the comparison between the experimental results (Qt) and the theoretical predictions (Qp) for atenolol at varying temperatures. The residual variations were small between the rates of ion-exchange and ionic reaction, suggesting that the ionic reaction was the rate-determining step for the loading process of ion-exchange fibers. However, for type two drugs at low temperature, the calculated values were somewhat higher than the observed ones, illustrating that there were other factors influencing the exchange rate under some conditions.

Bottom Line:
The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion.Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences.The drug-fiber complexes exhibited sustained release.

ABSTRACTIon-exchange fibers were different from conventional ion-exchange resins in their non-cross-linked structure. The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion. Therefore, this work aimed to investigate the load and release characteristics of five model drugs with the strong cationic ion-exchange fiber ZB-1. Drugs were loaded using a batch process and released in United States Pharmacopoeia (USP) dissolution apparatus 2. Opposing exchange kinetics, suitable for the special structure of the fiber, were developed for describing the exchange process with the help of thermodynamics, which illustrated that the load was controlled by an ionic reaction. The molecular weight was the most important factor to influence the drug load and release rate. Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences. The drug-fiber complexes exhibited sustained release. Different kinds and concentrations of counter ions or different amounts of drug-fiber complexes in the release medium affected the release behavior, while the pH value was independent of it. The groundwork for in-depth exploration and further application of ion-exchange fibers has been laid.